Signal seeking tuner with manufally wound driving spring



Sept. 1, 1959 E. F. ANDREWS SIGNAL SERKING TUNER WITH MANUALLY woUND DRIVING SPRING 2 Sheets-Sheet l Original Filed Nov. 15, 1950 NN EN N Jn wlw T.. I s, w RG M ww NR m@ RN N u NN I NQ NNN \l1\\ IIII mm t mw W wm QN I I\ Pf\ k TRE. ,mm Nh www I .9 mlw/ {QW/KN@ www Hw.. l QmIm N WN 0.5355 l l I N I I HNRG NG WSN n Q\N\ Qbm -u oRzoU I N t wz..m wkwbm if. www QN, n, w \J RR I f N3 GNN RW NN hun H v I www. .H ,NN R f* H W m' NI .Surzoyw N., NNN Cols m mm m u:3o w Wofls um .NN N\ www www NI A J @N 9N WN QW IVM NMWMV... NNN NNN www NMM/ QGNNILW I E? I. Joukzou mz. @mv W%\ H Emmi@ Sept. l, 1959 E. F. ANDREWS 2,902,599

SIGNAL sEEKING TUNER WITH MANUALLY woUND DRIVING SPRING original Filed Ney. 1s, 195o 2 Sheets-Sheet 2 RECEIVER COMPONENTS 2 7 la? f o United States Patent() SIGNAL SEEKING TUNER WITH MANUALLY WOUND DRIVING SPRING Edward F. Andrews, Belleair Beach, Fla., assignor, by mesne assignments, to General Motors Corporation, Detroit, Mich., a corporation of Delaware 6 Y Claims. (Cl. Z50-20) This invention relates to signal tuned radio apparatus. `Signal tuned radio receivers require no manual presetting to tune in progressively all transmitted signals of sufficient strength within the frequency tuning range of the receiver. Signal tuned radio apparatus has broad utility and is applicable to home receivers and other radio apparatus as well as automobile receivers and other receivers which are subject to frequent changes of geographical position.

Signal tuned receivers have also been known in the art asstop-on-signal, stop-on-carrier, or signal seeking receivers. Signal tuned apparatus of this general type has been described and claimed in other patents, such as those of E. F. Andrews Patent No. 2,493,741, issued January l0,` 1950, and O. Gierwiatowski Patent No. 2,494,235, issued January l0, 1950, and E. F. AndrewsPatent No. "2,541,018, issued February 13, 1951. `The present invention is applicable generally to resonant responsive electronic apparatus, but more specifically it constitutes an improvement on certain features of the signal tuned radio apparatus `described in the above mentioned patents. This application is a division of Serial No. 195,161 tiled November 13, 1950 which `issued as Patent No. 2,773,193 on December 4, 1956.

lt is one of the objects of this vinvention to provide certain advantages over and improvements lupon the structures shown in the patents above referred to. The solenoid, limit switch, and other parts associated with charg` ing the tuner operating spring by electrical power are Vitems of considerable cost. Occasionally they may also fail to operate properly in service. For instance, if the voltage of the car battery is suiciently reduced and the limit switch operates to energize the solenoid, the force produced by the solenoid at this low voltage may be insuiicient to eifect operation and instead of the limit switch interrupting the current it remains closed and the solenoid continues to draw a considerable current which could cause overheating and/or still further discharge of the storage battery. Although safeguards can be provided, they :add still rfurther to the cost.

According to oneof the features of this invention, economy and reliability can both be enhanced by providing means for recharging `the tuning drive spring manually at the end of each -frequency -band traverse or at any 'intermediate position. Manual recharging requires little effort and isnecessary only infrequently because ordinarily from ten to fifty stations can be tuned before the spring -must again be charged. Recharging may be performed by a further movement of the same control member which starts the tuner to tune in another station. This arrangement has the further advantage that -by an appropriate movement of the control member the tuner can be moved in the spring charging direction any amount desired and this movement can be initiated while the tuner `is in any intermediate position between the discharged and charged positions of the spring. With the structure shown in ice initiated by the solenoid until the high frequency or spring-discharged end of the scale has been reached, and then the tuner is ymoved all the way to the low frequency `or spring-charged end. During charging of the springs no means is provided for stopping at any intermediate position adjacent a desired station as can `be done by the proper manual operation of the manual tuning and `recharging control of this invention.

Likewise, with the solenoid recharged tuner, if the starting switch is inadvertently operated the tuner must go all the way to the high frequency end, all the way back to the low frequency end by `the action of the solenoid, and then from the low frequency end toward the'high 4frequency end to return to the desired station. lWith-the manual recharging control, `the control may be'moved a very small distance suflicient to pass to the low frequency side of t-he `desired station. lf the control is thenreleased the desired station will be immediately tuned in. If the operator knows the position of any desired station on the visual tuning scale, he can immediately tune it in in a single quick operation by this method. Experience has shown that this is often a very worth-while advantage, particularly when many stations of sufiicient strength-to operate the tuner are present across the band.

One object of the present invention, therefore, is tolprovide an improved signal tuned or .stop-on-signal radioapparatus. f

Another object is to provide an improved signal tuned radio receiver. t

A further object is to provide a new and improved signal tuned radio apparatus including variable tuning means, potential energy storage meansV for varying the tunling means, means `for terminating variation of the tuning means by the potential energy storage means in response to a signal tuned by the tuning means, and manually operated means `for recharging the energy storage means and for restarting the tuning means to tune in a diiferent signal. 'l'he energy storage means is preferably a stressed spring means, but may be of some other suitable type such as piston or bellows subject to fluid pressure oran elevated weight. i

A further object is to provide a compact, readily producible, `signal tuned device in which the tuning mechanism is driven in one direction by a spring or other suitable energy `storage means, and in which the energy storage means is recharged and the tuning mechanism simultaneously moved in the opposite direction by manually moving a charging, and positioning member. f

A further object is to provide a signal tuned device ,in which a small movement of a member causes the energy storage means to move the tuning means to tune in astation and a second small movement causes the tuning in of another staiton in the same Way, 'while a larger movement of the same member causes the energy storage ,Y means to be recharged.

vthe above `patents the spring `charging operation is not i A further object `is to provide a member .manually rotatable in one -direction to charge an energy storagemeans for varying the tuning means, and in which a short Aaxial movement of an associated member causes the energy storage meansto move the tuning means until the tuning means is signal tuned to another station, if the signal of a station is present and of required strength.Y

It is a further object to provide a signal tuned device with a member in which a short movement of the member effects the signal `tuning of successive stations by a resilient -driving means, and in which a larger motion of the member effects `the recharging of said resilient means, and in which two-directional manual tuning, as differentiated from signal tuning, is accomplished by motions `of `the `tuning member in opposite directions.

It is a further object to provide a signal tuned device, for instance any of those described in previous objects, with means byvwhich the resilient means for varying the tuner may be recharged to any desired degree by a smaller or larger manual movement of a tuning member, and in which the tuning means is moved in one direction a smaller or a larger distance corresponding to the movement of the tuning member. I

It is a further object to provide a signal tuned mechanism of the type previously described in which the tuner can be moved a desired distance in one direction and the tuner drive mechanism recharged not only when the tuner drive mechanism is completely discharged, but also at any intermediate position between charge and discharge.

, ings in which:

Figure 1 is a diagrammatic View of an illustrative signal tuned radio receiver constructed in accordance with the invention;

Figure 2 is a perspective view showing the external appearance of the receiver;

Figure 3 is a diagrammatic side elevational sectional View illustrating a modified embodiment;

Figure 4 is a fragmentary front elevational view illustrating the external appearance of the embodiment of Figure 3, a portion of the external wall of the receiver being broken away to illustrate mechanical details;

Figure 5 is a fragmentary elevational sectional View illustrating another modified embodiment;

Figure 6 is a fragmentary sectional view taken on line 6-6 of Figure 5; and

Figure 7 is a fragmentary elevational sectional View illustrating a modification of the embodiment of Figures 3 and 4.

Certain features of the apparatus disclosed in this application are not a part of this invention and will be disi closed and claimed in other copending applications.

The signal tuned radio receiver illustrated in Fig. l has many of the components of the usual superheterodyne receiver. It has a radio frequency amplifier 10 with an input. to which an antenna 12 may be connected. A superheterodyne converter stage 14 is coupled to the output of the RF. amplifier Iii. The converter 14 may include a first detector, an oscillator, and an I F. input transformer for coupling the output of the first detector to an intermediate frequency amplifier tube 16.

The output of the l.F. tube 16 is coupled to a diodetriode tube 18 which functions as the detector for listening and as the actuating voltage rectifier for signal tuning. The output of the detector tube 18 is coupled to a first f audio amplifier comprising a triode section of a second diode-triode tube 20, the diode section providing autol matic volume control voltage. The output of the triode section of the tube 20 is coupled by a capacitor 21 to a second audio amplifier tube 22 having an output transformer 24 in its plate circuit. The tubes 20 and 22 function as amplifiers during both listening and signal tuning. A speaker 26 is provided for listening.

vThe receiver includes a radio frequency tuning inductance 28, a first detector tuning inductance 30, and an oscillator tuning inductance 32 which are connected with the corresponding portions of the circuit by means of pairs of leads X, Y and Z, respectively. For convenience and clarity only the end portions of the leads are shown.

. The inductance coils 28, 30 and 32 are mounted with their axes parallel. The coils are tunable by means of cores or slugs 34, 36 and 38 which are movable in an K axial direction.

The tuning cores 34, 36 and 38 are mounted on a crossi piece 40 which is supported by a rack member 42. The

rack 42 is slidablv mounted on a supporting rod 44. The crosspiece is slidably guided by a pushrod or control 4 plunger 46 to restrain the rack from rotation on the supporting rod 44 and to maintain alignment between the cores 34, 36 and 38 and the coils 28, 30 and 32. A knob 48 is provided on the front end of the pushrod 46 for manually pushing the rod inwardly, and a helical return spring 50 is positioned around the pushrod to urge it outwardly. A C-Washer or abutment 52, mounted on the pushrod 46, is engageable with the front of the crosspiece 40 when the pushrod is pushed inwardly.

The rack meshes with a pinion 54. A coil spring 56 produces a clockwise torque on the pinion so as to urge the rack outwardly.

A spring pressed pawl 58 pivoted on a gear wheel 60 engages the pinion for transmitting clockwise rotation of the pinion to the gear 69. The gear 60 meshes with a pinion 62 fixed to a second gear wheel 64 which meshes with a pinion 66. The pinion 66 is fixed to a brake disc or stopping member 68. A wind vane 69 is carried by the stopping member 68 to control and stabilize the tuning speed by providing rapidiy increasing resistance to rotation of the stopping member as its speed increases.

VA relay 7@ has an armature 72 which isiurged toward the brake disc 68 by means of a spring 74. The tension exerted by the spring 74 may be adjusted by means of a screw '76.

The relay 70 has a pair of oppositely polarizable Windings 78 and 80, the winding 73 Yoperating to attract the armature 72 and the winding 80 operating to release the armature. The relay has a core 82 mounted in a frame 34. l The magnetic circuit formed by the core 82, the frame 84 and the armature 72 has considerable retentivity so that the armature may be retained in attracted position by residual magnetism, once it has been moved to attracted or closed position by energization of the winding 78. Energization of the winding 8i) releases the armature by bucking the residual magnetism.

The receiver is powered by a battery 86 which may be an automobile battery. The battery is utilized to energize the winding 76 for attracting the armature 72 to commence tuning. The attracting Winding 78 of the relay 70 is connected across the battery 86 through a starting switch 87 comprising a pair of contact springs 58 and 90. The contacts S8 and 90 are normally held open by engagement of the Washer 52 on the pushrod 46 with a spring member 92 mechanically connected with the contact spring 88 but electrically insulated therefrom. When the knob 48 on the pushrod is pushed inwardly, the washer 52 is disengaged from the spring member 92 and the spring member closes the contacts 88 and 90. The contacts are shunted by a bleeder resistor 94 which permits a small current to flow through the attracting Winding 78 when the contacts are open to augment the residual magnetism and to provide an adjustment ofv the force tending to bold the armature in attracted or closed position. If the bleeder current or the retentivity of the magnetic material is suitably increased, the relay armature may be moved to closed position by a directly applied manual movement if desired. Under these circumstances the closing winding and the starting switch would be eliminated.

Energy for tuning the receiver is stored in the coil spring S6 by manually moving the knob 48 on the pushrod 46 inwardly. This produces inward movement of the rack 42 and-rotates the pinion 54 counterclockwisey to tension Vthe coil spring. The pawl 58 ratchets over the teeth of vari-nature is heldin attracted position by residual magnetsm, magnetism produced by bleeder current through the resistor 94, or both. i

When a signal is tuned in, an impulse from the output transformer 24 is impressed upon the releasing winding 80 to counteract the effect of the residual magnetism momentarily and to release the armature 72. After the armature is released, it is again engaged with the brake disc 68 by the spring 74, and tuning is stopped on the signal.

The relay 70 operates switch means 99 including a number of movable contacts. A movable contact 100 is movable 4between stationary contacts 102 and 104 for connecting a secondary `winding 105 of the output transformer 24 with the speaker 26 when the armature 72 is released and with the releasing Winding`80 when the armature 72 is attracted. ri`hus the output transformer is connected with the speaker for listening and with the releasing winding for tuning.

The means for producing an impulse for stopping the tuning of the receiver on a signal will now be described.

Plate voltage for the receiver is applied by a vibrator B supply 106 having two B+ output conductors 168 and 118. The B supply 106 is connected with the battery 86 through a switch 112 and an interference filter comprising a series indu'ctance 114 and a pair of shunt capacitors 116 and 118.

An LF. output transformer 120 couples the intermediate frequency amplifier pentode 16 with the detector tube 18. The transformer 120 has a primary Winding 122 connected between the anode of the pentode 16 and the B supply conductor 108. The primary 122 is shunted by a capacitor 124 to form a tuned circuit.

A secondary tuned circuit comprising a secondary winding 126 in parallel with a capacitor 128 is coupled with the primary winding 122. One end of the tuned secondary winding `126 is connected to the anode 130 of the diode section of the tube 18. The other end of the secondary winding 126 is connected with the cathode of the diode-triode tube 18 through a series circuit including an intermediate frequency iiltering resistor 132, a volume control and diode load resistor 134, and a cathode load resistor 136. Two intermediate frequency bypass capacitors 137 are connected respectively between the ends of the filtering resistor 132 and ground.

The LF. output transformer 120 has an untuned secondary winding 138 which is closely coupled to the primary winding 122. The windings 122 and 138 may constitute a single winding of multiple strand Litz wire, some of the strands being used for the primary Winding 122 and others being used for secondary winding 188. A ferromagnetic core 143 axially movable within the winding 122 may be provided to tune the primary circuit, comprising the winding 122 and capacitor 124, to resonance. The secondary winding 126 may be carried in axially spaced relation to the Winding 122 and 138. A second ferromagnetic core 145 may be provided to tune the secondary circuit, comprising winding 126 and capacitor 128, to resonance. The coupling between the primary Winding 122 and the secondary winding 126 may be changed, for instance, by adjusting the axial spacing of the two windings.

One end of the untuned `secondary 138 is connected with the grid of the diode-triade tube 18, and the other end is connected to Iground through a resistor 139 shunted by a bypass capacitor 141. The triode section of the tube 18 is connected as an infinite impedance rectifier. The triode anode 140 of the tube 18 is connected directly with the B supply conductor 108 and is bypassed to ground by a capacitor 142. l111e resistor 136 serves as a load resistance for the triode section of the tube 18. This resistor also provides resistance coupling between the triode and diode circuits of the tube 18. The cathode is bypassed to ground through an intermediate frequency bypass capacitor 144. In order to furnish cathode bias voltages the conductor 146 which connects 1the volume control resistor 134 and the cathode load resistor 136 is connected with the B supply conductor 108 through a resistor 148.

A movable contact 152 operated by the relay armature 72 engages a stationary contact 154 to short out the cathode load resistor 136 when the armature is in its listening position in engagement with the brake disc 68. When the armature is in its tuning position the movable `contact 152 engages a stationary contact 156 to connect the conductor 146 with the junction 158 of the secondary winding 138 and the resistor 139 through a resistor 168. When the relay armature 72 is in listening position there is a large positive voltage on the cathode of the tube 18 supplied from lead 108 through the resistor 148, while the grid, which is connected to ground through resistor 139, is maintained substantially at ground potential.

When the relay armature is in` the tuning position the cathode load resistor 136 is in the circuit. A delay bias for the triode section of the tube 18 is developed by the voltage drop across the resistor 160, which now establishes bias on the grid relative to the cathode by raising the voltage at junction 158 above ground. The curent flowing from the B supply conductor 108 through the resistor 168 provides delay bias for the triode restraining voltage rectifier section of the tube 18.

The grid of the first audio amplifier triode section of the tube 20 is shunted to the cathode by a resistor 162. The grid is connected through a coupling capacitor 164 to a movable contact 166 operated by the relay armature 72. When the relay armature is in listening position, the movable contact 166 engages a stationary contact 168 connected with the slider 169 of the volume control 134. When the relay armature 72 is in the tuning position, the movable Contact 166 engages a stationary contact 170 connected with the diode plate end of the volume control resistor 134 by an interference filtering resistor 172 and shunted to ground by an interference bypasss capacitor 174. Thus different adjustments of the volume control have no eifect during tuning.

The tube 22 is connected as a power amplifier.` The output transformer 24 has a primary Winding 176 which connects the anode of the tube 22 with the B supply Iconductor 118.

A series circuit comprising a tone control capacitor 178 and a variable tone control resistor 180 is connected between the grid of the tube 22 and ground.

rhe tube 20 has a diode anode 182 which is coupled to the untuned secondary 138 through an intermediate frequency coupling capacitor 184. The anode 182 is connected to ground through a load resistor 186 and t0 an automatic volume control line conductor 188 through an automatic volume control filtering resistor 190. A bypass capacitor 192 connects the AVC line 188 to ground. rEhe AVC line is connected with the RI". ampliier 18, the rst detector forming a part of the converter stage 14, and through the LF. input transformer with the grid of the LF. pentode 16.

It is advantageous for both listening and tuning to prevent operation of the AVC on weak signals. This may be accomplished by providing a delay bias to prevent operation of the AVC rectifier at low signal inputs. By this means the full sensitivity of the receiver is available at low signal inputs while at high signal inputs the AVC operates in the usual manner to hold the output at a substantially constant level.

A cathode resistor 194 is connected between the cathode of the diode-triode tube 2t) and ground. The cathode is connected through a voltage dividing resistor 196 shunted by a capacitor 198 to the conductor 146 and thence through the resistor 148 to the B supply conductor 108. The voltage drop across the resistor 194 provides an AVC delay bias.

The cathodes of the radio frequency amplifier tube and the first detector tube are brought out by conductors 200 and 202 which are connected to ground through a vari- .ablesenstivty .controlresistor 20,4 shunted by a bypass capacitor 206. The conductors 200 and 202 are connected `witha stationary contact 208 on the .relay 70 which is shorted to ground by a movable contact 210 when the relay armature 72 is in listening position .so that ,the sensitivity control is effective only during tuning.

ln the operation of the receiver, the spring 56 may be .charged initially `=by manually pressing the knob 48 on theipushrod 46 inwardly. The rack l2 is thereby moved rearwardly .and the `cores 34, 36 and 38 are moved into their respective coils 28, 30 and 32. The knob 48 is promptly released after `it is moved inwardly. The attracting winding 78 closes the relay when the inward motion ofthe ,pusghrod 46 permits the spring member 92, to close the .contacts 88 *andV 9.0. Thus the relay armature 72 is attracted and the brake disc is released. The confacts :88 and 90 are opened when the pushrod is released, since the .return spring 5.0 overcomes the force of the spring member 92.

vThe .armature 72 is retained in attracted position Yby residual .magnetism and/ or by the magnetic field produced by the current through the bleeder resistor 94 passing through the attracting Winding 78.

. The spring ,56 rotates the pinion 54 and thereby moves the rack 42 forwardly. Since the cores 34, 36 and 38 are moved out `of their respective coils the receiver is tuned toward the high frequency end of the tuning range.

Returning now to the signal tuning circuits, as stated above, the coupling between the primary 122 and the secondary 1,26 is adjusted by moving one of the coils to increase or decrease the axial distance between them. A degree of coupling between these coils which gives very good results may be secured in the following manner. First, the grid-.cathode bias of the tube 18 should be adjusted so that the plate current of the tube is at cutoff with -zero signal input. Then with a signal of moderate strength applied to the grid of the tube 16, the coupling is adjusted so that there is an appreciable voltage output from the diode section of the tube 18, measured, for instance, across the volume control resistor 134. The coupling is then reduced until this voltage substantially disappears. This means that the restraining voltage developed across the resistor 136 and applied to the plate 130 is Vsubstantially equal tothe voltage applied to the plate 130 `from the coil v126.

Next, the bias between the cathode and the grid of the tube 1'8 is increased by `three or four volts to provide a delay bias. With :this additional bias applied tothe restraining voltage triode rectifier, an actuating voltage will appear across the resistor 134 as long as a signal :is applied, for instance, to the grid of the tube 16, as previously described. The voltage across the resistor 134 will increase as the applied signal increases until the appliedsignal equals the delay bias, after which there will be no further substantial voltage increase. Since the voltageoutput does not increase further with strong signals the Width of the signal in terms of frequency does not undergo a further increase and both strong and weak signals are tuned closely to the center LF. frequency.

The tuning response characteristic of the untuned secondary winding 138 is like that of the primary 122 and issornewhat broader than the response characteristics of the secondary tuned circuit comprising the winding 126 and the capacitor 128. The response of the untuned circuit should not be narrower than that of the tuned circuit. Consequently as a signal is approached a substantial signal voltage first tends to develop across the secondary 138 and then rises gradually in magnitude along a broad response curve. The signal voltage across the secondary 138 is applied to the grid -of the triode section of the tube 18 to produce a positive rectified output voltage across the cathode load resistor 136 when the signal exceeds the delay bias supplied by the voltage drop across the resistor 160.

lAs the receiver `is tuned more'closely tothe signal by the spring 56, a signal voltage begins to develop across the more sharplyftuued secondary winding 1126. Since the load resistor 13.6 yis fin series with the circuit connecting the diode plate .-130 ,to the cathode ofthe tube 18, the rectiiied vsignal voltage across the resistor 136, due t0 the triode infinite .impedance rectifier, Vbiases the cathode positively with respect -to the diode anode 130 and there` by restrains rectification by the diode until the voltage across the tuned secondary 126 exceeds the bias, due to the triode rectifier, ,-across the resistor 136. The .drop across Ythe resistor y116,0.1caused by `current .from ,the B supply,-provides ,a delay bias which holds the grida few volts negative relative Ito the cathode of the triode ,section of the tube 18. This delay .bias `prevents rectification inthe trioderectifier yand thus delays the build-up of the positive .restraining voltage until the signal across the secondary 138 exceeds the delay bias. The restrain-v ing voltage retarded by the delay bias prevents strong stations from producing a tuning signal much higher and wider :than Jthe weaker stations, and together .they provide relatively luniform response of the actuating circuit to signals of varying magnitude.

-When the diode section of the tube 18 begins to icon.- duct, a signal impulse is transmitted to the grid of the first audio triode section of the tube 20 through the static .filtering resistor 172, the contacts and 166, and the .coupling capacitor `164. It will be seen that although the signal from the vdiode section of the tube 18 follows the pathithrough thestatic filter during tuning and through the volume -control resistor 134 and slider 169 during listening, as determined by ythe position of the switch contact166, `the tuning and the listening signals nevertheless come from the same diode and also from the V'same tuned circuit consisting of the'irzductance 126 and capacitor 128. As a result, the last tuned circuit that establishes the frequency for signal tuning is also the last tuned circuit which establishes the frequency of the signal Vduring listening. Although during tuning the widthV of the response of this tuned circuit is narrowed, particularly tovstrong signals, the center frequency is the same as during listening. This eliminates possible error in tuning which might occur if a diffe-rent tuned circuit were employed for tuning and listening, where one circuit could get out of tune with respect to the other.

The impulse is amplified by the first audio triode and the power vamplifier tube 22 and is supplied to the relay releasing winding 80 by the secondary 105 of the output transformer '24.` This Aimpulse is of relatively low frequency and, therefore, it is .desirable that the output transformer be of such construction as to provide effective power output at low frequencies. For similar reasons, the coupling condenser 21 should also be of sufficient capacity. A resistor 175 and a capacitor 177 are provided to improve sensitivity and proper relay action. The secondary of the output transformer and the releasing winding -80 are polarized with respect to the attracting winding 7,8 so that the first signal impulse through the releasing winding bucks or counteracts the residual magnetism and/or the magnetism caused by the current in the attracting winding 78 through bleeder 94. If the impulse is of suii'icient strength, the relay armature 72 ,is released and tuning vis discontinued by engagement gf thg armature with the brake disc or stopping mem.-

The magnitude of the holding Current through the bleeder resistor v9A is one of the factors determining the ,sensitivity of the relay 70. The sensitivity generally is increased .if the bleeder current is decreased. The retentivity of the core 82, the Varmature 72 and the frame 84, as well as the strength or adjustment of the armature spring 74, lalso affect the sensitivity.

The adjustment of the sensitivity control resistor 20.4 determinesl the strength of the signal necessary for `stopping the tuning of the receiver on a signal. The operation of the tuning mechanism is not affected by the setting of the volume control resistor 134 because the slider 169 of the volume control is disconnected during tuning, and the signal output is taken through the interference filtering resistor 172 from the end of the volume control resistor connected with the diode anode 130. During tuning, the resistor y172 and the capacitor 174 provide additional filtering to minimize the possibility of the tuner being stopped by static or other interference. This filter does not appreciably affect the audio response during listening.

When the relay armature 72 has been released to stop the tuning the movable Irelay contacts shift to their listening positions. The movable contact `210` shorts out the sensitivity control resistor 204 so that the full sensitivity of the receiver controlled by the AVC is available for listening.

During listening the movable contact 152 shorts out the cathode load resistor 136 to prevent any signal volt ages from developing across this resistor, and to permit the full signal voltage to develop across the volume control resistor 134. The triode section of the tube 18 is cut off by disconnecting the resistor 160 from the posi tively changed conductor 146, thus permitting the grid ofthe triode section to drop to ground potential. The conductor 146 is at-a positive potential high enough to effectively prevent rectification in the triode restraining `"voltage rectifier with the strongest sign-al input.

For listening, the movable contact 166 connects the input of the first audio tube 20 to the slider 169 of the` `volume control resistor so that the slider Vmay be ad- #immediately below the pushrod 46. The volume control Aresistor 134 and the battery switch 112 may becontrolled by a knob 218, and the tone control resistor 180 may i be controlled by a ring 216.` The sensitivity control may be controlled by a knob 217 and the'receiver maybe conditioned for manual or signal tuning by means of a lever 219. The receiver maybe enclosed in a housing automobile. t

Manyof the advantages of the embodiment `of the invention illustrated in Figures l and 2 have already been discussed. Recharging the spring 56 by pushing 220 and maybe adapted for mounting'o'n the dash of Van The pushrod or control plunger 46 protrudes theknob on the control plunger inwardly requires little manual effort sincetliespring need be strong enough only to insure reliable starting. Recharging of the spring is Vnecessary only after the entire tuning range has been traversed. This occurs infrequently since several stations spaced across the tuning range will ordinarily have suicient strength for signaltuning in most localities.

-If the station whichis desired is inadvertently passed during signaltuning by accidentally tapping the control knobthe knob may bepressedinwardly `to move the 'tuning `cores reversely a short distance just beyond the 'station accidentallypassed'. The amount the tuning cores `are moved and the amount the spring is recharged aredetermined by the extent ofthe inward movement of the `control knob. yIf the tuning cores have been moved manually some distance to the low `frequency side of a desired station; thestation may be tuned in by tapping the control knob repeatedly until the station is heard. fllhe receiver dial may be observed during this progcedure if the station cannot be identified by ear.

' lf the location of a desired station on the dial is known,

the station may be tuned in4 quicklyY by pushing the :control knob `inwardlyjtoV tune the receiver to a point slightly onthe low frequency side of 1thedesired sta-` tion as indicated on the dial. The desired station then be signal tuned when the knob is released.

During signal tuning, the driving spring 56 continuously maintains a torque upon the pinion 54 and thereby takes up any slack in the gearing connecting the pinion With the stopping member 68. This feature substantially prevents any slack in the gearing from causing inaccurate signal tuning.

If desired, the apparatus of Figures l and 2 may be modified slightly so that the driving spring also takes up any slack which may exist between the rack 42 and the pinion 54. This may be done by providing a separate pinion meshing with the rack 42. 'Bhe torsional driving springs 56 is then connected to this separate pinion which drives the rack during tuning, taking up the play between the pinion 54 and the rack 42. The rack may be lengthened or otherwise modified for this purpose. A straight tension helical spring may also be employed acting linearly on the rack. Such a spring should be extended a long distance from zero tension position compared to the change in length that the spring undergoes in moving the rack from one end of its travel to the other.

A modified form of the invention is illustrated in Figures 3 and 4. The modification relates particularly to the relay controlled spring operated mechanism for driving the tuning elements of the receiver. The other components of the receiver may be the same as in the embodiment of Figures l and 2. These components are indicated in Figure 3 by a box 350.

The embodiment of Figure 3 includes the relay 70 as described above. The attracting winding 7S of the relay is energized from B supply terminals 352 of the receiver through a starting switch 354 having a pair orf normally spaced apart contact springs 356 and 358.

The embodiment of Figure 3 includes the stopping member or brake disc 68, the pinion 66 and the wind vane 69 mounted on the shaft 226 as previously described.

The pinion 66 meshes with a gear wheel 360 carrying a spring pressed pawl 362 which engages. a pinion 364. The gear wheel 360 and pinion 364 are coaxial and independently rotatable. The pinion 364 meshes with a gear wheel 366 mounted on a hub 368 which is rotatable on a shaft 370. A spring 372, coiled around the hub 368, has its opposite ends secured to the gear wheel 366 and a stationary part of the tuning means 374. The shaft 370 is the control shaft of a variable gang condenser or other tuning means 374 forming a part of the receiver.

A control knob 376 supporting a radial indicator 378 is fixed to the outer end of the shaft 370. As shown in Figure 4 the indicator is rotatable along a graduated dial 380.

The knob 376 is engageable with the gear wheel 366 by means of a pin 382 which may be inserted into a single aperture 384 in the gear wheel. A spring 386 coiled `around the pin and compressed between the knob andan abutment Washer 388 urges the pin toward engagement with the gear wheel 366. It may be disengaged by sliding the pin manually outwardly, and the pin may be retained The starting switch 354 is operable by means of a push button 396 which may be supported at the center of the outer face of the knob 376 by means of a plurality ozf rods 397 extending longitudinally through the knob. A ring 398 positioned around the shaft 370 is secured to the inner ends of the rods 397. When the push button `3196 is pushed inwardly, the ring 398 engages the front contact spring 358 of `the starting switch for closing the latter.` The spring of the contactmoves it normally into *the open switch'position. The push button may be mountknob 376 in a clockwise direction. This rotates the pinion 364 in a counterclockwise direction. The pawl 362 is free to ratchet over the pinion so that the gear wheel 360 does not have to rotate. Consequently the armature 72 of the relay may remain in contact with stopping member 368 during charging of the spring. In order to charge the spring the pin 382 must be engaged with the 4aperture 384 in the gear wheel 366.

Rotation of the knob 376 to charge the driving spring 372 also produces rotation of the tuning sha t 370 and thereby moves that tuning means 374 toward one end of its tuning range. The knob 376 may be rotated suiciently to move the tuning means all the way to the end of its tuning range or only partway, as desired.

The change in the tension of the spring, produced by charging the spring, is relatively small with respect to the initial tension on the spring. Consequently the torque exerted by the spring is relatively constant throughout the tuning range of the receiver.

` When the driving spring 372 is charged, the push button 396 may be tapped to close the starting switch 354 momentarily. This energizes the attracting winding 78 of the relay and releases the relay armature 72 from the stopping member 68 to commence tuning, as previously described in connection with the embodiment of Figures 1 and 2. During tuning the gear wheel 366 drives the pinion 364 in a clockwise direction so that the pawl 362 ,is carried along to produce rotation of the gear wheel 360,

the stopping member 68 and the wind vane 230.

VAs indicated, the releasing winding 80 may be connected with the receiver components indicated by the box 350 in the same manner as in the embodiment of Figures .1 and 2. The relay 70 of the embodiment of Figure 3 operates the switch means 99 as previously described.

When a signal of suicient strength is tuned in, an im pulse is impressed upon the releasing winding 80 to release the relay armature 72 and stop the brake disc 68. With respect to stopping, the pawl 362 forms a positive driving connection between the pinion 364 and the gear 360 so that the stopping of the brake disc 68 stops the tuning accurately on the signal.

The driving spring 372 maintains a torque upon the gear wheel 366 when the tuning is stopped on a signal so that any slack in the gear train is taken up.

When manual tuning is desired the pin 382 may be withdrawn from the gear wheel 366 as previously described. Rotation of the knob 376 then produces rotation of the tuning shaft 370 without charging the spring 372 or rotating the wind vane or brake drum. When the pin 382 is withdrawn, the spring driven tuning mechanism is entirely disconnected from the tuning shaft 370 so that it ofers no resistance to the rotation of the knob 376.

In the event that the relay armature 72 releases the stopping member 68 while the pin 382 is withdrawn, the engagementof the stopping pin 393, on the gear 366, with the abutment 39S prevents complete unwinding of the spring 372 so that an initial tension is maintained on the spring. The gear stops at a position corresponding to one end of the tuning range of the receiver.

Other features of the construction and operation of the embodiment of Figure 3 which have not been specifically described may be the same as described in connection with the embodiment of Figures 1 and 2.

An embodiment representing a further modification is illustrated in Figures 5 and 6. This embodiment is similar to the embodiment of Figures 1 and 2 and Figures 3 and 4 in many respects. The embodiment of Figures 5 and 6 includes tuning vmeans 399 which may be varied by rotating a shaft 401. A gear wheel 400 is mounted on a hub 402- which is fixed to the shaft 401. The gear `vpinion 62 lillustrated in Figure l.

A knob 404 is rotatable on the outer end of the shaft 401. A spring 406, coiled around the shaft 401, has its opposite ends attached to the gear wheel 400 and the knob 404. The knob is slidable inwardly against the resilient resistance of the spring 406 to engage the contact spring 358 and thereby close the starting switch 354.

The gear wheel 400 may mesh with a gear Wheel 408 for operating an indicator of any suitable type.

A ratchet wheel 414 is iixed to the knob 404. A relatively long chisel pointed pawl 416 is movable into engagement with the ratchet wheel 414 for selectively restraining either clockwise or counterclockwise rotation of the knob. The pawl remains in engagement with ratchet wheel 414 due to gravity. The pawl is mounted on one end of a shaft 418 rotatably supported in a bushing 410 carried on a panel plate 412,. the pawl being positioned on the front side of the panel plate. A pin 420, fixed to the pawl 416, is provided for moving the pawlmanually into its Various positions. An eccentric cam 422 is tixed to the other end of the shaft 418. This cam is provided with a notch 424.

A bracket 426 carried by the panel member 412 may be provided to support a rod member 428 for axial movement. A washer 430 is fixed to the rod 428. A compression spring 432 operates between one bracket member 434 and the washer 430 to urge the rounded end of the rod 428 toward the surface of the cam 422. A knob 436 is carried on the end of the shaft 401 and may be 1 secured to the shaft by a set screw 438.

For manual operation the pawl 416 is disengaged from the ratchet wheel 414 and is moved into a vertical position as viewed in Figure 6. Movement of the pawl 416 rotates the cam 422 which engages the end of the rod 428 and moves it upwardly against the force of the cornpression spring 432. When the pawl 416 reaches a vertical position the end of the rod 428 drops into the notch 424 in the cam 422. The force of the spring 432 holds the end of the rod 428 in engagement with the notch 424 in the cam 416 to retain the cam and the pawl 416 in position.V The rod 428 in Figure 5 operates to disengage the armature 72 of the relay 70 from the brake member -68 to permit free rotation of the gear train. However,

wheel 40o.

In another mode of operation of the embodiment the pawl 416 may be rotated from its vertical position to a position where the end of the rod 428 drops into a notch 440 in the cam 422. In this position the rod 428`moves downwardly to permit the relay armature 72 to effectively engage'the brake disc 68. When the knob 404 is rotated in either direction, the spring 406 is charged. While the knob is held in twisted position, it is moved inwardly momentarily to close the starting switch 354 for releasing the'relay armature 72 from the brake disc 68 to commence tuning movement of the shaft 401 by the spring 406. The tuning is stopped on a signal when an impulse from the receiver releases the relay armature as previously described. Thus the receiver may be manually tuned in either direction to lthe next adjacent station having suispring may be wound in.k either direction depending upon whether the p awl is positioned to restrain clockwise or counterclockwise rotation of the ratchet wheel 414.

When the spring is charged, the knob 404 may be moved inwardly momentarily to close the starting switch 354 and thereby to initiate movement of the tuning shaft 401 by the spring 406.

In some cases the shaft 401 for varying the tuning means 399 may be continuously rotatable. This may be the case when the tuning means comprises straight-line capacitance variable capacitors. Continuous rotation of the tuning means in a receiver having such capacitors `varies the tuning across the entire tuning range alternately in opposite directions. A scale may be employed with graduations extending over a complete 360 of angular motion. If, for instance, a variable condenser is employed which can rotate only 180, a corresponding scale or dial may be used. When the tuning shaft 401 is`continuously rotatable, the knob 404 may be wound to charge the spring 406 to an extent sufficient to vary the tuning throughout several traverses across the tuning range. quently.

Figure 7 illustrates a modified form of the signa1 tuned radio receivershown in Figures 3 and 4.l The modification of Figure 7 permits manual tuning at any time during signal tuning without the operation of any disconnecting member such as the pin 382 in Figure 3. Moreover signal tuning can be resumed after manual tuning without requiring any separate operation other than the Vtuning operation itself to effect the change.

In Figure 7 the tuning means 374 of the receiver has a rotatable control shaft 450 which corresponds generally with the shaft 370 shown in Figure 3. A knob 452 is fixed to the shaft 450. A spring 454, coiled around the shaft 450, has its opposite ends iixed to the shaft and to a stationary portion of the tuning means 374 respectively. The dial indicator 378 may be secured to the knob 452. For greater accuracy of manual tuning `the knob 452 may be made larger. If desired a tuning scale my be marked on the knob and a stationary index provi ed.

A gear 456 has a hub 458 which is rotatably mounted on a stern 460 formed on the rear of the knob 452. A coil spring 462 is compressed between the gear 456` and a collar 464 fixed to the rear end of the stem. The spring urges the gear into engagement with a flange 466 on the knob 452. In the modification of Figure 7 the gear 360 and the pinion 364 of Figure 3 are iixed together, for instance, by staking the gear 360 directly to one end of the pinion 364. The ratchet 362 is omitted. The push button 396 for operating the starting switch may be mounted on the panel of the receiver. Other details of the receiver of Figure 7 may be the same as the embodiment of Figures 3 and 4. The gear 458, which replaces the gear 366 of Figure 3, may mesh with the pinion 364. The compression of the spring 462 may be such that when the armature brake 72 is applied by the spring 74 the fraction of the slip joint will be sui'icient to hold the shaft 450 in any position to which it is turned against the maximum torque of the spring 454. However, this friction should be insuiicient to cause the slippage of the armature brake 72 when it is applied and the knob 452 is turned manually.

For signal tuning, the operation of the receiver illustrated in Figure 7 is similar to the operation of the embodiment of Figures 3 and 4. To minimize variation of spring torque over the entire tuning range, the spring 454 is given several turns so that its initial or minimum tension is large compared with the change in tension from one end to the other of the tuning range. The spring 454 tends to rotate the tuning shaft 450 in one direction which may be counterclockwise as viewed from the front of the receiver. The tension on the spring 454 is increased by manually rotating the knob 452 in the opposite direction. When the spring 454 is being manually charged the gear 456 is not rotated because the frictional drive between ,the gear and the flange 466 on the knob Thus winding or recharging is required less fre- 14 slips. Consequently the relay armature 72 may remain in contact with the brake disc 68 during charging Aof the spring.

When the spring 454 rotates the shaft 450 during signal tuning, the gear 456 turns with the knob 452 because the spring 462 is strong enough rto provide sufficient friction between the gear and the ilange 466 to prevent slippage ot the gear. The gear 456 drives the stopping member 68 and the wind vane`69 until the stopping member 68 is stopped by the relay armature 72. The accuracy of the tuning is not affected by the frictional connection between the gear 456 and the knob 452 because the spring 462 is strong enough to prevent slipping when the tuning is stopped on a signal. Signal tuning is started by tapping the push button 396 as in the embodiment of Figures 3 and 4.

For manual tuning, the knob 452 is turned to rotate the tuning shaft 450 to the desired position. When the knob 452 is turned in either direction to charge the spring 454 or to relieve tension on the spring, the knob slips with respect to the gear 456. Thus manual tuning may be accomplished although the relay armature 72 remains "in contact with the brake disc 68 and holds the gear train stationary. The strength of the spring 462 is such that a moderate amount of manual effort is sufficient to produce vslipping between the knob 452 and the gear 456 so that the gear may remain stationary while the knob is rotated. The receiver illustrated in Figure 7 has the advantage that either signa1 tuning or manual tuning can be accomplished without operating any changeover control. The receiver is manually tuned by merely rotating the knob 452 to the desired position. During manual tuning, the contacts operated by the relay 70 remain in their listening position. For signal tuning the spring is charged by rotating the knob manually, and then signals are tuned 1n by tapping the push button 396.

While I have shown and described several preferred embodiments of my invention, it will be apparent that numerous variations and modiiications thereof may be made without departing from the underlying principles of the invention. l therefore desire, by the following claims, to include within the scope of the invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

l. In radio receiving apparatus movable tuning means for tuning the apparatus over a predetermined band of frequencies, power storage means connected to the movable tuning means to move the same in either direction depending upon which direction it is charged, indexing stopping means operatively engageable with the movable tuning means and connected to the receiving apparatus to stop the tuning means upon receipt of an incoming signal in the receiving apparatus, manually movable means connected directly to said power storage means to charge the same and adjustable locking pawl means mounted adjacent the manually movable means and the indexing stopping means to selectively mechanically position a part of the indexing stopping means and to engage and lock the position of the manually movable means to maintain the power storage means loaded.

2. ln radio receiving apparatus movable tuning means for tuning the apparatus over a predetermined band of frequencies, power storage means connected to the movable tuning means to move the same in either direction, indexing stopping means operatively engageable with the movable tuning means and connected to the receiving apparatus to stop the tuning means upon receipt of an incoming signal in the receiving apparatus, manually movable means connected to said power storage means to manually tune the apparatus through said power storage means and pawl means pivotally mounted adjacent said manually movable means and movable to engage the manually movable means and lock the same so that the power shaft to turn the same to scan the band of frequencies,

manually rotatable means loosely mounted on the shaft and connected to the powerstorage means and xedly mounted pawl means engageable with the manually rotatable means to prevent rotation of the manually rotatable means after it has been turned to load the power storage means in one direction to maintain the load on the power storage resilient means for driving the shaft.

4. In radio receiving apparatus having movable tuning means, a rotatable shaft connected to the movable tuning means, power storage resilient means connected to the shaft to turn the same to scan a frequency band, manually rotatable means loosely mounted on the shaft and connected to the power storage means and pawl meansr selectively engageable with the manually rotatable means to prevent rotation of the manually rotatable means after it has been turned to load the power storage means in either selected direction to maintain the load on the power storage means to drive the movable tuning means in either desired direction.

5. In radio receiving apparatus having movable tuning means, a rotatable shaft connected to the movable tuning means, power storage resilient means connected to 16 the shaft to turn the same to `scan a frequency band, manually rotatable means loosely'rnounted on the shaft and connected to the power storagemeans, ixedly mounted ratchet means engageable with the manually .rotatable means to prevent its rotation in one direction and latch means engageable with the ratchet means to retain it'out of engagement with the manually rotatable `means so that the shaft maybe turned manually.

6. In radio receiving apparatus having movable tuning means, a rotatable shaft connected to the movable tuning means, power storage resilient means connected to the shaft to turn the same toscana frequency band, manually rotatable means loosely mounted on the Yshaft and connected to the power storage means to load the power storage resilient means, locking means for the manually rotatable means to maintain the load on the power storage means after the manually rotatable means has been turned to load the same and a second manual control means rigidly connectedY to said shaft to independently turn the same.

References Cited in the file of thisY patent UNITED `STATES PATENTS Sperber Apr. 19, 

